Injection molded light pipe

ABSTRACT

An injection molded light pipe having a sharp curve is proposed, wherein the injection molding mark is on the inside surface of the sharp curve. The light pipe has a 180° curve with a radius of curvature less than approximately 3 times the diameter of the light pipe.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to a copending U.S. application Ser. No.08/778,001 filed Dec. 31, 1916 (now U.S. Pat. No. 6,201,880), which isincorporated herein by reference in its entirety including incorporatedmaterial. This application is related to an application by the sameinventors deposited on the same day as the present application entitled“Apparatus for holding optical instruments in a reproducible positionwith respect to teeth”. This application claims priority pursuant to 35U.S.C. 119(e) to U.S. Provisional Applications: Application No.60/167711 filed Nov. 27, 1999 which is incorporated herein by referencein its entirety including incorporated material.

FIELD OF THE INVENTION

The field of the invention is the field of imaging of teeth in a mouth.

BACKGROUND OF THE INVENTION

The above identified U.S. patent application summarizes the backgroundof the art of imaging of teeth in great detail. In brief, the prior artto the above identified application is deficient in that images of teethtaken with light transillumination were not reproducible. The aboveidentified application teaches that the illumination source and imagingsystem must be held in a reproducible and repeatable position withrespect to the tooth by anchoring the source and imaging systemphysically with respect to the tooth. The above identified applicationteaches that the light for illumination may be piped around in tightconfines in a mouth using a light pipe material.

SUMMARY OF THE INVENTION

The present invention is a light pipe apparatus which has little losseven while incorporating sharp bends. The light pipe is injection moldedusing a suitable substance which is transparent when solidified. Theinjection mold point is at the inside of a curve of the light pipe. Theinvention has a light pipe apparatus with a light pipe with a sharp 180°bend for taking light from a handpiece, moving the light to a positionto direct light from the end of the light pipe back towards and opticalimaging system in the handpiece so that the light impinges on a toothplaced between the end of the lightpipe and the imaging system of thehandpiece.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B show the spring prongs of the invention removed from andin place against proximal surfaces of a tooth.

FIGS. 2A and 2B show the most preferred spring prongs of the inventionremoved from and in place against proximal surfaces of a tooth.

FIG. 3A and 3B show side views of the spring prongs of the invention inplace against a proximal surface of a tooth when the most preferredembodiment of the invention is rotated.

FIG. 4 is a drawing of an alternative embodiment of the invention

FIGS. 5A-5C are the drawings of an embodiment of the invention.

FIG. 6 is a drawing of an embodiment of the invention.

FIG. 7 is a drawing of an embodiment of the invention.

FIG. 8 is a drawing of an embodiment of the invention.

FIG. 9 is a drawing of an embodiment of the invention.

FIG. 10 is a drawing of a disposable mouthpiece of the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1A shows a sketch of a body 10 having two prongs 12 and 12′attached. The prongs are near but do not touch a tooth 14 in a row ofteeth. FIGS. 1A and 1B are shown looking at the top of the teeth in abottom row of teeth as an example. As the body 10 moves towards thetooth 14 so that the ends of the prongs 12 and 12′ touch the tooth 14,the prongs 12 and 12′ elastically separate at the distal ends andcontact the proximal surfaces of the tooth 14 at positions 16 and 16′.The body 10 is then held in a repeatable position with respect to tooth14 so that a source of illumination 18 connected to body 10 may radiatelight rays 17 on to the surface 19. The source of illumination 18 may bea light pipe, a laser, or a light emitting diode (LED), or other lightsource as known in the art. Prongs 12 and 12′ are preferably long thinplates having thickness t, length l, and height h (not shown) in orderthat the prongs 12 may act as springs to hold teeth of differentdimensions in a reproducible way.

FIGS. 2A and 2B show the prongs of the most preferable embodiment of theinvention. A U shaped plate 22 is joined to the body 20 at one end, andprongs 24 are joined to the U shaped plate 22 at the other end. When theprongs 24 and 24′ are brought into contact with and pressed againsttooth 14, the prongs 24 and 24′ separate until the distal ends of theprongs lodge in the V shaped space between the tooth 14 and theneighboring teeth. Prongs 24 and 24′ are shown having cylindricallyshaped ends 26 and 26′ for this purpose. Proximal surfaces (next to theneighboring teeth) 27 and 28 and labial or buccal surfaces 25 and 29 oftooth 14 are shown. The U shaped plate allows for a greater springdisplacement while holding the illumination source 18 near the tooth 14.It is important the prongs open at a slight angle as noted in FIG. 2a sothat there is a moment arm about the pivot points at the ends of the Uto open the prongs when the prongs are pushed against the tooth. As theend of the prong slides against the tooth towards the proximal surface,another moment arm opens the U to give a large displacement of thedistal end of the prong.

FIGS. 3A and 3B show a side view of the tooth 14 with prongs 12 holdingillumination source 18 in place. Body 10 is shown having a surface 30resting on the occlusal surface 32 of tooth 14. The combination ofprongs 12 contacting the proximal surfaces of tooth 14 and the body 10touching surface 32 of the tooth holds the illumination source 18 forrepeatable imaging of the tooth. Light rays 34 are shown incident on thetooth 14, and light rays 36 which have been transmitted by the tooth 14are shown exiting from the opposite face of the tooth to impinge onmirror 37. Mirror 37 is held fixed with respect to body 10. Light rays36 are shown reflected from mirror 37 to mirror 38, which is fixed withrespect to a handle 39. Light rays 36 are reflected from mirror 39 to animaging system (not shown) which produces an electronic image of tooth14 using transilluminated light through the tooth 14. Body 10 isrotatably connected to handle 39 so that rotating body 10 around an axis35 fixed with respect to handle 39 allows imaging of both the labial(FIG. 3A) and buccal (FIG. 3B) surfaces of tooth 14.

FIG. 4 shows an alternative embodiment of the invention, where theocclusal surface 41 of the tooth 14 is imaged through handle 48 whilethe body 40 is held in a reproducible position with respect to tooth 14by means of spring prongs 42. The prongs 42 may be held in the V shapedgrooves between tooth 14 and neighboring teeth in a reproducibleposition with respect to the gum line 44.

In the all the forgoing embodiments, the body 40 may or may not rest ona surface of the tooth as long as the prongs hold the body in areproducible position with respect to the tooth. For some applications,the reproducibility of the angle of illumination and imaging issufficient to obtain reproducible images with just the prongs contactingthe proximal tooth surfaces. For instance, the operator may hold thebody so that the prongs contact the proximal surfaces of the teeth andalso the gum line. The inventors have found that image quality is muchenhanced if the tooth is illuminated low on the tooth towards the gumline. In adults, the best results are obtained if the tooth isilluminated 4 to 7 mm from the incisal or occlusal surface, and moreparticularly 5-6 mm, while in children the best results occur forillumination 4 to 5 mm from the incisal or occlusal surface of thetooth.

If a portion of the body is in contact with the occlusal surface 41 ofthe tooth 14 in FIG. 4, at least a portion of the body must betransparent or shaped to allow light to propagate from the tooth throughthe body to the imaging system. Note that rotating (not shown) body 40about axis 46 allows imaging of the same occlusal surface, but withillumination from different sides of the tooth.

Handles 39 and 48 are typically hollow tubes shaped for conducting lightfrom a mirror 38 to an imaging system contained in a handpiece (notshown) which connects removably to the handle 39 or 48. FIGS. 3 and 4are drawn looking from the handpiece down the handle at a mirror 48 or38 fixed with respect to the handle. Light is also conducted from thehandpiece to the body for illumination in the most preferred embodiment.A light pipe (position shown later) in the handpiece is in closeproximity to a light pipe connected to the body.

FIGS. 5A-C show plan, side and end elevation views of an innovativesolution to the problem of moving light around in the tight confines ofa mouth. Light is brought from the handpiece by a lightpipe in positionshown by the dotted outline 56 into light pipe 50 through face 51 andexits through face 52. Lightpipe 50 is connected to the body 10. Thelightpipe 50 perferably is round with a cross sectional area A, but itmay have a square, rectangular, oval, or other cross section as is knownin the art. The light pipe has a length 1measured along the curvingaxis. The light pipe is long enough that l²>>>A. The light pipe 50 isbent approximately 90° at position 53, and approximately 180° atposition 54, so that light is piped around and sent back towards thehandle 39. This innovative light pipe ensures that the light source andthe imaging system for the transillumination may both be contained inthe same handle which is introduced into the mouth.

Rotation of lightpipe 50 and 50′ about axis 35 brings lightpipe 50′ inposition to receive light when the body 10 rotates 180° about the handle39.

In order that light pipes 50 and 50′ may be made inexpensively, theyshould be made by injection molding of a suitable polymer material. Itis important that the injection mold mark be placed in a position tominimize light loss in a light pipe which has such tight turns, wherethe radius of curvature R of the light pipe is less than 10 A^(½). Suchpositioning is even more important when the radius of curvature R of thelight pipe is less than 3 A^(½) The inventors have found that injectionmolding where the injection takes place on an inside curve of the lightpipe such as at position 53 and 54 noted on FIG. 5A and 5C produces alight pipe which scatters less light, and that such injection moldedlight pipes are the most preferable light pipes for the invention. Theinventors have found that acrylic light pipes, where the index ofrefraction of the acrylic is 1.49, may support a 180° curve of radius ofcurvature 3 mm for a light pipe 1.6 mm in diameter.

FIG. 6 shows that the light pipe end faces 62 and 62′ may be formed inthe shape of a D, so that the spots of light from the two light pipesmay be closer to the center of the tooth. Light pipes 72 and 72′ areshown with such end faces in FIG. 7.

FIG. 8 shows a modification of the prongs of the invention in case asingle tooth is to be imaged. Detents 80 and 80′ in the prongs 82 and82′ grasp the tooth 84 on proximal surfaces.

FIG. 9 shows a sketch of an embodiment of the invention where theillumination source 98 illuminates the occlusal surface of the tooth 14while the tooth 14 is held by prongs on the labial or buccal side, andthe other labial or buccal side is imaged by the imaging system.

FIG. 10 shows a perspective sketch of the handle and the rotatable bodyof the present invention.

Obviously, many modifications and variations of the present inventionare possible in light of the above teachings. It is therefore to beunderstood that, within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described.

We claim:
 1. A light pipe, comprising: an extended transparent bodyhaving a substantially constant cross sectional area A along an axis oflength l, where l²>>>A, and wherein the axis has approximately 180°first curve with a radius R<10A^(½), and wherein the body has a flatfirst end face approximately perpendicular to the axis for introducinglight into the body, and a flat second end face approximatelyperpendicular to the axis for the light to exit the body and shine lightback in the direction of the first end face.
 2. The light pipe of claim1, wherein the second end face is in the shape of a D.
 3. The light pipeof claim 1, wherein the extended body has a second approximately 90°curve near the first end face, and wherein the first and second curvesare in approximately perpendicular directions.
 4. The light pipe ofclaim 3, wherein the second end face is in the shape of a D.
 5. Thelight pipe of claim 4, wherein a second light pipe with a shapesubstantially a mirror image of the first light pipe is mounted with thetwo D faces in close proximity so that light piped through both lightpipes irradiates a surface in two spots of close proximity.
 6. The lightpipe of claim 1, wherein the body is produced by injection molding, andwherein an injection molding mark is on the surface of the body at theinside of the curve.
 7. The light pipe of claim 6, wherein the extendedbody has a first end and a second end with end faces substantiallyperpendicular to the axis, and wherein the first end face is in theshape of a D.
 8. The light pipe of claim 6, wherein the extended bodyhas a first end and a second end with end faces substantiallyperpendicular to the axis, and wherein the body has a first U shapedcurve through approximately 180° at the first end and a secondapproximately 90° curve at the second end, and wherein the first andsecond curves are in approximately perpendicular directions.
 9. Thelight pipe of claim 8, wherein the first end face is in the shape of aD.
 10. The light pipe of claim 9, wherein a second light pipe with ashape substantially a mirror image of the first light pipe is mountedwith the two D faces in close proximity so that light piped through bothlight pipes irradiates a surface in two spots of close proximity.